The present invention relates to a control device for an engine provided with electromagnetic driven intake valves and more particularly to the control device for an engine provided with electromagnetic driven intake valves that is constructed to control a super lean burn by operating a valve opening and closing timing of the electromagnetic driven intake valve and the control method therefor.
The Official Gazette of JP-A-63-147957 discloses a technique of achieving an engine brake effect and reducing torque shock and pumping loss by changing an opening and closing timing of electromagnetic driven valves. The technique disclosed in this Official Gazette is constructed to set the valve timing of an intake valve to a normal timing during a fuel cut period in a decelerating time and change the valve timing into a early closing timing immediately before the end of the fuel cut (restart of the fuel supply). Since the valve opening and closing timings are alternately changed between the two timing modes, that is, the normal timing and the early closing timing, the early closing timing constantly set during the fuel cut period may disadvantageously causes the pumping loss to be too much reduced, thereby making the engine brakes effect insufficient.
The JP-A-9-88645 has proposed a technique that is constructed to overcome the foregoing disadvantage. This technique uses electromagnetic driven intake valves for more fine adjusting a valve opening period in a predetermined fuel-cut driving condition, thereby reducing the pumping loss and achieving a proper engine brake effect. The technique disclosed in JP-A-9-88645 has proposed the reduction of the torque shock and pumping loss in the fuel-cut driving condition or the like by changing the opening and closing timing of the electromagnetic driven valve, concretely, an opening timing of the valve. However, the technique has no special proposal on a lean burn engines and a system for controlling the lean burn engines for improving combustion efficiency of the engine.
In the current field of engines for automobiles, it is more expected to reduce the fuel consumption. Hence, various techniques have been proposed for controlling an A/F (air-fuel ratio) of an engine so that the engine may adopt a lean burn method. As a technique of relating the A/F control to intake and exhaust valves, the JP-A-10-82333 discloses a technique provided with a valve timing varying device for varying an opening and closing timing of at least one of the intake and the exhaust valves according to the A/F. The JP-A-3-74547 also proposes a technique for changing a fresh air rate according to change of the valve timing. This technique is constructed to correct a fuel supply by changing an engine A/F according to the opening and closing timing of the intake and the exhaust valves.
On the other hand, in order to adjust an engine A/F, it is necessary to adjust the opening and closing time of the intake and the exhaust valves according to some factors such as an engine speed and load. Also, in order to improve a combustion state for giving an influence on an engine output, it is necessary to adjust an intake speed of air flowing into a cylinder, that is, the influence caused by swirl or tumble of suction air generated in the cylinder.
However, though the technique disclosed in JP-A-3-74547 is constructed to relate the A/F control with the intake and the exhaust valves, the technique does not consider the swirl generated inside of the cylinder. Moreover, it does not take into consideration the relation between the action of the intake and the exhaust valves and the swirl when controlling the A/F.
It is an object of the present invention to a control device for an engine provided with electromagnetic driven valves which is constructed to adjust intake air sucked into the cylinder of the engine and a sucking speed by controlling an opening and closing timing, a valve opening time, and a lifting amount in the valve opening and thereby to stabilize a super lean burn in the engine for controlling an A/F, and a control method for the engine.